Series of i-beams



G. H. BLAKELEY 5511155 OF I-BEAMS Filed {April 6 192] 3 Sheets-Sheet 5Ew u 15 load carrying capacity of t Patented May 27, 1924.

U N ET SERIES OF I-BEAMS.

- Application filed April 6,

T all whom it may concern:

Be it known that I, GEORGE H. BLAKELEY,

a citizen of the United States, and residing at Bethlehem, LohighCounty, State of Pennsylvania, have invented certain new and usefulImprovements in Series of I- Beams, of which the following is aspecifica tion. The present inventionrelatesto rolled I- beams, theprincipal object being to provide an improved series of I-beams, theheavier beams of the series having a load carrying capacity per unit ofweight per foot sub stantially the same as, or reater than the helighter beams of the series.

Heretofore, a series of standard I-beams, say inch beams, has consistedof a plurality of beams of the same depth-except variations due to theexigencies of manufacture. The beams of the prior series vary in weightfrom the lightest to the heaviest of the series, the increase in weightbeing obtained by separating the rolls, thus increasing the thickness ofthe web and the width across the flanges by the same amount. Hence theonly variablesin a series of the prior art are the thickness of the weband the width across the flanges. In a series of this kind the strengthof the beams per pound per foot of length does not increase as fast asthe weight.

In manufacturing" beams on standard mills, the rolls wear rapidly sothat relatively large tolerances in the dimensions of the finished beamsare permitted. Thus a 15 inch beam may be 14% inches to- 151 inchesdeep. the tolerances of this particular series being such as to permit avariation of inch under or 9; inch over the nominal size. In otherwords, when a purchaser obtains a 15 inch beam, it will not necessarilybe 15 inches deep but may measure anywhere from 14% inches to 153;inches-deep.

In alike manner other series of beams may vary in depth within certainother limits.

These variations or tolerances'are necessary for practical andcommercial reasons. As stated, the rolls are adjusted toward each otherin order. to decrease the weights of the beams of a series. The amountsby which the rolls are adjusted are unchan ed for certain periods oftime. During t is 1921. Serial No. 458,876.

time, the rolls wear, so that, whereas the first beam rolled might be 11i; inches deep, a beam'rolled near the end of said period n'light be15- inches deep. At the endof the period these rolls are removed to bedressed down and others substituted. If closer tolerances weremaintained it would be necessary to shut down the mill at more frequentintervals for the purpose of changing rolls, thereby greatly increasingthe cost of manufacture. It is the aim of the present invention toutilize the aforementioned variation in depth for the purpose ofproviding another variable in the series of beams; that is to say, inthe series of the present invention the depth is also varied within thelimit of the tolerances heretofore allowed. For this purpose the beamsof my, series are manufactured more accurately, the tolerances being cutdown to substantially nothing. In other words, a 15% beam of the presentseries is as nearly 152; inches as can be obtained. Hence any beam in aseries of the present-invention can be used where a beam from thecorresponding old series would have been employed. The greater accuracyin rolling may be obtained by finishingthe beams on a universal mill.

The present invention therefore comprises I a series of I-beams ofdifierent weights, in which the ratio of section modulus to weight perfoot in a heavy beam is'substantially the same as (or greater than) thecorresponding ratio in a lighter beam; the depths of the beams of theseries increasing progressively from the lightest to the heaviest butthe total difierence in depth betweenthe lightest and the heaviest beamsbeing relatively small; the section moduli of the beams of the seriesincreasing progressively from the lightest to the heaviest bysubstantial amounts. I

Other objects and features of novelty will be'apparent from thedescription taken in connection with the drawings in which:

Figs. 1 to 5 inclusive are transverse sectional views of a. series offive I-beams embodying the .present invention;

ing the method now in common use of in creasing the sectional areas in aseries of I- beams from the minimum to the maximum size;

Fig. 12 is a diagrammatic sketch showing the method of increasing thesectional area in myimproved series of I-beams from the minimum to themaximum size.

The customary fillets at the junctions of the flanges and the webs andthe rounding of the inner edges of the flanges have been omitted fromthe drawings.

In the design of steel structures, when the approximate maximum depthavailable and the load a beam is to carry are known, it is apparent thatas a matter of economy a beam of the greatest depth less than the saidmaximum and of the lightest weight which will carry the load withsafety, should be selected from commercial standards. A series of beamsof different weights is therefore provided to permit the architect to select, if practicable, from commercial standards a beam having the loadcarrying capacity (or section modulus) desired. and still keep withinthe limit of maximum depth. In all series of I-beams of the prior art,the percentage of increase in weight of the heavier beams over thelighter beams is far in excess of the percentage of increase in loadcarrying capacity resulting therefrom.

To constitute a series of beams as the term series is herein used, allthe beams of the group must have a common slope a of inner flange facesand a common dimension L (see Fig. 11) the latter dimension being theshortest distance between inner flange faces measured along the websurface. This requirement is due to considerations of roll economy, allthe beams of a given series being normally produced on the same oridentical sets of rolls. If the above mentioned slope oz and dimension Lwere varied, the resulting multiplicity of rolls would greatly increasethe cost of production. Fig. 11 shows diagrammatically, in anexaggerated degree, the -method followed in the prior art for increasingthe sectional area and weight of the I-beams of a series from theminimum to the maximum sizes, the full lines indicating the minimumsection, and the full and broken lines indicating the maximum section.It will be observed that the depth D is the same for all sections, as islikewise the length of the flange leg F, or the minimum distance betweenthe web surface and the extreme edge of the adja-' cent flange tip.

In the series of 15" standard I-beams shown in Figures 6 to 10 inclusiveit will be observed that the dimensions L, F, and the angle a areconstant throughout, and respectively equal to 13.33", 2.545 and 9" 28Likewise referring to Figures 1 to 5 inelusive, it will be observed thatin the new series of I-beams which I have invented, the dimension L andthe angle are kept constant throughout, and in the particular I- beamsillustrated are respectively equal to 13.33" and 9 28. It'will also beobserved that the dimension F is the same for all beams of the seriesand equal to 2.545, but the invention is not limited to having thisdimension constant in all beams of a series. The principal structuraldifference between my improved series of I-beams, and the I-beams of theprior art, resides in the progressive increase in depth from thelightest to the heaviest I-beams by relatively small increments.Referring to the drawings it will be observed that, the depth of theit'- beam in Fig. 1 is 15", the depth of beam in Fig. 2 is 15%,, thedepth of beam in Fig. 3 is 15% the depth of beam in Fig. 4 is 1.5 anddepth of beam in Fig. 5 is 15%". In the practice commonly followed inthe rolling of Lbeams a tolerance of under, and 1 3; over, nominal depthis allowed, and in some cases it is not unusual to increase thistolerance to under, and 3;" over, nominal depth. It will be observedtherefore that the difference in depth between the I-beam shown inFigure 1 and the I-beam shown in Figure 4 does not exceed the toleranceallowed by common practice, and the difference in depth between the I-beam shown in Fig. 1 and the I-beam shown in Fig. 5 does not exceed themaximum tolerance permissible. As will be shown hereafter, by thuslimiting the difference in depth between the minimum and the maxi mumweight of beam in my improved series to substantially the toleranceallowed by commonvpractice, and maintaining the dimension L constant, Isecure, as compared with the heavier beams of a series of the prior art,a considerable increase in load carrying capacity for a given weight ofbeam, or for the same load carrying capacity a considerable saving inweight. This follows from the fact that in my series the thickness ofthe flanges is varied, thus permitting the metal of the heavier beams tobe disposed in its most etlicient location.

The section modulus of an I-beam is the quotient resulting from dividingthe moment of inertia of the section with respect to an axisperpendicular to the neutral fibre by one-half the depth of the beam,and the maximum. safe bending moment an I-beam may withstand isproportional to its section modulus. The relative strengths of two beamstherefore, is directly proportional to their section moduli. and ameasure of the load carrying capacity per unit of weight is thereforegiven by the quotient obtained by dividing the section modulus by theweight of the ll-beam per unit of length. The section moduli of thesections indicated llt) in Figs. 6 150 10 inclusive may be computed fromthe dimensions given, and are respectively as follows:

pound per foot of these I-beams are given by the quantities:

In the improved series of I-beams which I have invented having thedimensions indicated in Figs. 1 to 5 inclusive, the section moduli areas follows:

and the corresponding weights per foot of length are,

and their relative load carrying capacities per pound per foot are givenby the quantit-ies, a a

Comparing the lightest and the heaviest beam of the series of theI-beams of the prior art having the dimensions indicated in Figs. 6 and10 respectively, it will be ob served that the increase 1n weight of theheaviest over the lightest beam is approximately 43%, while thecorresponding increase in section modulus is only 22%. On the otherhand, in my improved series of I- beamsto obtain an increase of 22% insection modulus I find it necessary to increase the weight of thesection by only 22%.

Beams of the type shown in Figs. 1 to 5 inclusive may be produced in thefollowing manner. A beam having dimensions the same as or slightly inexcess of the dimensions of the heaviest beam of the series may beproduced on an ordinary standard rollin mill. This beam may be usedeither as the heaviest beam of the series, or it may be used as a blankto form the remaining beams of the series. In the latter case the webthickness,

beam blan would be fed into a universal mill and theweb and flangesproportionately reduced to the extent indicated in the figures.

It will be observed from the particular embodiment of my invention,illustrated in Figs. 1 to 5 inclusive. that the ratio of web thicknessto flange thickness is substantially the same for all beams of theseries, but I do not wish to limit myself to a series of beams havingthis constant ratio. Obviously in the design of' the heavier beams ofthe series the increase in flange thickness may be proportionatelygreater than the increase in thereby giving a relatively weights ofthese I-bearhsl face,

greater load carrying capacity per unit of 1 weight of beam. Likewise,in the design of the heavier beams of the series the increase in webthickness may be proportionately vslightly greater than the increase inflange thickness, and the resulting series of beams may stillhave asubstantially constant load carrying capacity per unit of weight.

Although the dimensions of a series of 15 inch I-beams' have beenillustrated in the drawings, and theinvention has been described inconnection with such a series, it is to be distinctly understood thatthe invention is not thus limited but applies to t -er series of beams.

Having thus described the invention what I claim as new and desire tosecure by Letters Patent is:

1. A series of I-beams of different weights,

the depths of individual I-bcams increasing progressively from thelightest to the heaviest, the total difference in the depth between thelightest and heaviest beams being relatively small, each beam havingsubstantially the same load carrying capacity per unit of weight perunit of length, and the increment in load carrying capacity between twosuccessive beams being a substantial amount.

2. A series of I-beams of different weights, the depths of individualI-beams increasing progressively from the lightest to the heaviest, thetotal difference in depth between the lightest and heaviest beams beingnot substantially greater than the usual rolling tolerances; the heavierbeams of the series having a unit of weight per unit of length not lessthan the lighter beams of the series, and the increment in load carryingcapacity between two successive beams being a substantial amount.

3. As an article of manufacture, an I- beam having the same nominalheight as the lightest of a series of standard beams but being heavier,the length of the flange legs, the shortest distance between the innerflange faces measured along the web surface, the slope of the innerflange faces, being substantially the same for both beams, the sectionalmodulus of the heavier beam being greater.'and the ratio of the meanthickness of the flanges to the thickness of the web being substantiallythe same for the two beams.

4-. As an article of manufacture, an I- beam having the same nominalheight as the lightest of a series of standard I-beams, but beingheavier, the length of the flange legs, the shortest distance betweeninner flange faces measured along the web surthe slope of the innerflange faces and the ratio of the mean flange thickness to the webthickness being substantially the same for both beams, and the sectionalload carrying capacity permodulus of said new beam per unit of weightper unit of length being not less than for said lightest beam.

5. As an article of manufacture, an I- beam having the same nominalheight as the lightest beam of a series of standard beams, but beingheavier, the ratio of the mean flange thickness to the web thicknessbeing substantially 1.5 for both beams.

6. As an article of manufacture, an I- beam having the same nominal heiht as the lightest of a series of standard Lbeams, but being heavier,the slope of the inner flange faces and the ratio of the mean flangethickness to the web thickness being substantially the same for bothbeams, and the sectional modulus of said new beam per unit of weight perunit of length being not less than for said lightest beam.

7. As an article of manufacture, an E- beam having the same nominalheight as the lightest of a series of standard lf-beams,

tween the inner flange faces measured along the web surface and theratio of the mean flange thickness to the web thickness beingsubstantially the same for both beams and the sectional modulus of saidnew beam per unit of weight per unit of length being not less than forsaid lightest beam.

In testimony whereof I hereunto affix my signature.

GEORGE H. BLAKELE Y.

